Anesthesiologists use dozens of different drugs, but they fall into a handful of core categories: drugs that put you to sleep, gases that keep you asleep, painkillers, muscle relaxants, and a supporting cast of medications that prevent nausea, maintain blood pressure, and reverse everything at the end of surgery. Most general anesthetics involve at least four or five drugs working together, each doing a specific job.
Drugs That Put You to Sleep
The first drug you’ll notice is the one pushed through your IV to induce unconsciousness. This happens fast, usually within 30 to 60 seconds. The most common induction agent is propofol, a white milky liquid that produces rapid, smooth loss of consciousness. It’s the default choice for most healthy patients undergoing routine surgery.
Two alternatives get used in specific situations. Etomidate is favored when blood pressure stability matters, such as in patients with heart problems or those who are critically ill, because it causes less of a drop in blood pressure than propofol. Ketamine takes a different approach entirely. Rather than simply sedating the brain, it blocks a specific receptor involved in pain signaling, which means it provides both unconsciousness and pain relief simultaneously. Ketamine also tends to support blood pressure rather than lower it, making it useful in trauma cases or when a patient is already in shock.
Inhaled Gases That Maintain Anesthesia
Once you’re asleep, anesthesiologists typically switch to an inhaled anesthetic gas delivered through a breathing circuit to keep you unconscious for the duration of surgery. The three main agents are sevoflurane, desflurane, and isoflurane. Sevoflurane is the most widely used because it’s gentle on the airways and doesn’t irritate the lungs, which also makes it the go-to choice for mask inductions in children. Desflurane wears off the fastest, which can be an advantage in longer surgeries where a quick wake-up is desirable, though it can irritate the airway if used for induction. Isoflurane is the oldest of the three and still sees use, particularly where cost is a consideration.
Each gas has a different potency, measured by the concentration needed to keep 50% of patients from moving in response to a surgical incision. Sevoflurane requires about 2% concentration in adults, desflurane needs roughly 6%, and isoflurane falls around 1.2%. These numbers don’t reflect how “strong” the drug feels to you; they just tell the anesthesiologist how much to dial in on the vaporizer.
Pain Medications Used During Surgery
General anesthesia makes you unconscious, but it doesn’t automatically block pain. Anesthesiologists add powerful opioid painkillers to blunt the body’s stress response to surgery and keep your heart rate and blood pressure from spiking when the surgeon makes an incision.
Fentanyl is by far the most common intraoperative opioid. Compared to morphine, fentanyl is roughly 58 times more potent by weight, which means tiny doses produce significant pain relief. It also works within a minute or two when given through an IV and wears off relatively quickly. Sufentanil is even more potent (about 423 times morphine’s strength) and gets reserved for major procedures like cardiac surgery. Remifentanil, at roughly 13 times morphine’s potency, has a unique property: your body breaks it down in minutes regardless of how long the infusion runs, so it’s ideal for surgeries where the anesthesiologist wants precise, moment-to-moment control of pain relief with a rapid wake-up afterward.
Muscle Relaxants
Many surgeries require complete muscle relaxation, both to make intubation (placing a breathing tube) easier and to give the surgeon a still, relaxed surgical field. These drugs paralyze skeletal muscles by blocking signals at the junction between nerves and muscle fibers.
Succinylcholine is the fastest-acting option, producing complete paralysis within about 60 seconds. It’s a short-acting drug, wearing off in 5 to 10 minutes on its own, which makes it popular for rapid-sequence intubations in emergencies when the anesthesiologist needs quick airway control. The tradeoff is a list of potential side effects including muscle soreness and, rarely, a dangerous rise in potassium levels.
Rocuronium is the most commonly used alternative. At a standard dose, it produces conditions suitable for intubation within about 1 to 2 minutes and provides roughly 30 to 35 minutes of muscle relaxation, with a wide range depending on the individual (anywhere from 15 to 85 minutes). Unlike succinylcholine, rocuronium’s effects can be precisely reversed at any point with a specific antidote, which has made it increasingly popular.
Drugs That Reverse Anesthesia Effects
At the end of surgery, any remaining muscle relaxation needs to be fully reversed before the breathing tube comes out. Two reversal agents are used. Sugammadex works by physically wrapping around rocuronium or vecuronium molecules and trapping them, effectively neutralizing the paralysis at any depth of blockade. Current practice guidelines from the Anesthesia Patient Safety Foundation recommend sugammadex over the older alternative for reversing deep, moderate, or shallow levels of muscle relaxation.
Neostigmine, the older option, works by a different mechanism: it increases the amount of the body’s natural nerve-signaling chemical at the muscle junction. It’s effective but only when the paralysis has already worn off significantly on its own. Guidelines consider neostigmine a reasonable alternative only when the blockade is already minimal. The preference for sugammadex in most situations reflects its ability to produce faster, more complete reversal and reduce the risk of residual weakness after surgery.
Local and Regional Anesthetics
Not every procedure requires general anesthesia. For nerve blocks, epidurals, spinal anesthetics, and local wound infiltration, anesthesiologists use a separate class of drugs that numb specific areas of the body. Lidocaine is the most familiar, with a maximum safe dose of 4.5 mg per kilogram of body weight (or up to 7 mg/kg when combined with epinephrine, which slows absorption). It works quickly and lasts one to two hours depending on the site and whether epinephrine is added.
Bupivacaine is the workhorse for longer-lasting regional anesthesia, providing numbness for several hours from a single injection. Its maximum dose is lower than lidocaine’s, at 2.5 mg/kg without epinephrine and 3 mg/kg with it, because it carries a higher risk of cardiac toxicity if accidentally injected into a blood vessel. Ropivacaine is a newer relative of bupivacaine with a somewhat better safety profile for the heart, making it a common choice for continuous nerve block infusions that may run for days after major joint or abdominal surgery.
Anti-Nausea and Anxiety Medications
Postoperative nausea and vomiting is one of the most common complaints after surgery, and anesthesiologists routinely give preventive medications before you even wake up. Ondansetron, typically given at 4 mg toward the end of surgery, blocks serotonin receptors in the gut and brain that trigger nausea. Dexamethasone, a steroid given at induction in doses around 4 to 8 mg, provides a second line of anti-nausea protection through a different mechanism and also helps reduce inflammation and swelling at the surgical site.
Midazolam, a fast-acting sedative in the benzodiazepine family, is commonly given before surgery to ease anxiety. A small dose through your IV produces calm and mild amnesia within a minute or two, which is why many patients don’t remember being wheeled into the operating room. Interestingly, midazolam also has some anti-nausea properties of its own.
Drugs for Blood Pressure Support
Anesthesia commonly causes blood pressure to drop, and anesthesiologists keep vasopressors on hand to correct this. Phenylephrine constricts blood vessels to raise pressure and is particularly favored during spinal anesthesia for cesarean deliveries, where studies show it has less effect on the baby’s blood acid levels compared to ephedrine. Ephedrine works differently: it both constricts blood vessels and stimulates the heart to beat faster and harder, making it useful when low blood pressure is accompanied by a slow heart rate. In high-risk cesarean cases involving conditions like preeclampsia, the evidence doesn’t clearly favor one over the other.
Sedation Without Full Anesthesia
For procedures that don’t require full unconsciousness, anesthesiologists can provide sedation that keeps you relaxed and comfortable while still technically arousable. Dexmedetomidine stands out in this category because it produces sedation that mimics natural sleep. It works by blocking the release of norepinephrine (the body’s alertness chemical) in the brainstem, producing calm, sleepiness, and mild pain relief without significantly suppressing breathing. This makes it valuable for procedures where the patient needs to be sedated but still breathe on their own, or in the ICU where patients may need days of light sedation.
Emergency Drugs
Certain rare but life-threatening reactions require immediate treatment. Malignant hyperthermia is a genetic condition in which specific anesthetic gases trigger an uncontrolled rise in body temperature, muscle rigidity, and metabolic crisis. The antidote is dantrolene, given intravenously at 1 to 2 mg/kg and repeated every 10 minutes until symptoms improve. Japanese guidelines cap the dose at 7 mg/kg, but Western guidelines recommend exceeding 10 mg/kg if the drug is working and symptoms persist, with no fixed upper limit as long as the clinical picture demands it.
Beyond dantrolene, every anesthesia cart contains epinephrine for anaphylactic reactions, atropine for dangerously slow heart rates, and a lipid emulsion solution that can rescue patients from local anesthetic toxicity by pulling the drug out of heart tissue. These drugs are rarely needed, but their immediate availability is a core part of anesthetic safety.